1 files changed, 47 insertions, 0 deletions
diff --git a/src/bytes/equal_test.go b/src/bytes/equal_test.go
new file mode 100644
index 000000000..1bf19a74b
--- /dev/null
+++ b/src/bytes/equal_test.go
@@ -0,0 +1,47 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// +build linux
+
+package bytes_test
+
+import (
+	. "bytes"
+	"syscall"
+	"testing"
+	"unsafe"
+)
+
+// This file tests the situation where memeq is checking
+// data very near to a page boundary.  We want to make sure
+// equal does not read across the boundary and cause a page
+// fault where it shouldn't.
+
+// This test runs only on linux.  The code being tested is
+// not OS-specific, so it does not need to be tested on all
+// operating systems.
+
+func TestEqualNearPageBoundary(t *testing.T) {
+	pagesize := syscall.Getpagesize()
+	b := make([]byte, 4*pagesize)
+	i := pagesize
+	for ; uintptr(unsafe.Pointer(&b[i]))%uintptr(pagesize) != 0; i++ {
+	}
+	syscall.Mprotect(b[i-pagesize:i], 0)
+	syscall.Mprotect(b[i+pagesize:i+2*pagesize], 0)
+	defer syscall.Mprotect(b[i-pagesize:i], syscall.PROT_READ|syscall.PROT_WRITE)
+	defer syscall.Mprotect(b[i+pagesize:i+2*pagesize], syscall.PROT_READ|syscall.PROT_WRITE)
+
+	// both of these should fault
+	//pagesize += int(b[i-1])
+	//pagesize += int(b[i+pagesize])
+
+	for j := 0; j < pagesize; j++ {
+		b[i+j] = 'A'
+	}
+	for j := 0; j <= pagesize; j++ {
+		Equal(b[i:i+j], b[i+pagesize-j:i+pagesize])
+		Equal(b[i+pagesize-j:i+pagesize], b[i:i+j])
+	}
+}